A Mississippi man was arrested on Wednesday, accused of sending letters to President Barack Obama and a senator that tested positive for poisonous ricin and set the nation's capital on edge a day after the Boston Marathon bombings.
Paul Kevin Curtis, 45, was arrested at his apartment near the Tennessee state line east of Memphis, said FBI Special Agent in Charge Daniel McMullen. It wasn't immediately known where he was being held.
Authorities still waited for definitive tests on the letters to Obama and Republican Sen. Roger Wicker of Mississippi. Preliminary field tests can often show false positives for ricin. The letters were intercepted before reaching the White House or Senate. Ricin is derived from the castor plant that makes castor oil. There is no antidote and it is at its deadliest when inhaled.
An FBI intelligence bulletin obtained by The Associated Press said the two letters were postmarked Memphis, Tennessee.
Both letters said: "To see a wrong and not expose it, is to become a silent partner to its continuance." Both were signed, "I am KC and I approve this message."
In Corinth, a city of about 14,000 in northeastern Mississippi, police cordoned off part of a subdivision where Curtis may live. Police on the scene would not confirm why they had blocked a few roads and set up a crime scene in the area of brick, single-family homes. At least five police cars were on the scene.
As authorities scurried to investigate three questionable packages discovered in Senate office buildings, reports of suspicious items also came in from at least three senators' offices in their home states.
Democratic Sen. Carl Levin said a staff member at an office in Michigan would spend the night in a hospital as a precaution after discovering a suspicious letter. The staff member had no symptoms, Levin said in a statement. He expected to learn preliminary results of tests on the letter by Thursday.
Republican Sen Jeff Flake said suspicious letters at his Phoenix office had been cleared with nothing dangerous found. A package at Sen John Cornyn's Dallas-area office also was declared harmless.
All three packages in the Capitol complex turned out to be safe, Capitol police spokeswoman Makema Turner said late Wednesday.
Senate Sergeant-at-Arms Terrance Gainer said that an individual who was responsible for the suspicious packages in the Hart and Russell Senate office buildings on Tuesday was detained and released on Wednesday. The packages were not hazardous.
Gainer said the man was "not particularly harmful, although terribly disruptive."